If you have an IPhone 13pro- current version or Samsung s23 ultra - s25 ultra. Consider looking into Freewell's creator kit.
They have a camera like handle that clamps onto your phone to give it a camera like feels (Bluetooth capable shutter button). And a phone specific case with a 17mm threaded filter attachment. So that way you can add ND Filters (Natural Diffusion Filters) and/or CPL filter (Circular Polarized)
I got both Filters and stacked them for the best of both worlds.
Anyway, check them out if youre interested.